Arctic Soil Releases Dangerous Levels of CO2, Speeding Global Warming

First Posted: Feb 12, 2013 09:31 AM EST

For most of the year, the Arctic is frozen: its hard-packed tundra and ice forming solid ground. In fact, some of that ice never melts in what is known as permafrost, which stays solid all year. Now, global warming has caused scientists to worry as permafrost melts, releasing a vast amount of CO2 into the atmosphere and further perpetuating the problem.

Flooding triggered by melting snow washes vast amounts of carbon-rich soil from the land into the water. These waters contain most of the carbon that is currently being released from melting permafrost. Permafrost itself contains years of collected organic matter and when it collapses, it exposes new layers of soil to sunlight. Once this carbon is exposed, it is then oxidized by bacteria and produces CO2. In fact, scientists estimate that carbon from surface waters amounts to as much as 40 percent of the total carbon that gets transferred from the Arctic to the atmosphere.

Yet there's more to the permafrost story than meets the eye. Rose Cory, an environmental scientist at the University of North Carolina, and colleagues collected samples of water trickling out of seven Alaskan thermokarst failures into nearby lakes and streams. They then analyzed these samples for colored dissolved organic matter. The closer to the terrestrial source, the more color the carbon will have. In addition, the scientists exposed the samples with ultraviolet light at six of the sites.

They found that ancient permafrost carbon was extremely reactive when exposed to the elements. The conversion of soil carbon to carbon dioxide and its release into the atmosphere was faster than scientists first predicted. The study also found that ultraviolet rays in sunlight both break down carbon, which makes it suitable for microbial consumption, and stimulates soil-dwelling bacteria.

The study has huge implications for climate change. It shows that melting permafrost can have a large impact on releasing CO2 into the atmosphere, and can function as a "positive feedback" that amplifies the issue.

The findings were published in the Journal Proceedings of the National Academy of Sciences.

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